Oil burner



OIL BURNER Filed Dec. 19, 1957 SWITCH SOLENOID OPERATED ON AND OFF VA'LVE )0 ,AlR MOTOR INSULATION A BELLOWS TYPE -AIR CONTROL 7 VALVE PREHEATER INVENTOR. 'BERTRAM B. REILLY.

ATTOR N EYS.

United States oIL BURNER This invention is for a burner for the burning of fuel oil, and relates more especially to the heating of the oil at and in advance of the burner nozzle.

Fuel oil, particularly fuel oil used for industrial purposes and industrial heating, is a mixture of hydrocarbons, some of which are exceptionally heavy, with the result that the fuel is difiicult to atomize and burn in an oil burner. Moreover, it is difficult to ignite with an electric spark igniter which it is desirable to use, and requires gas or light oil flame pilot burners. This is especially true in oil burners used in space heating where the heater usually operates intermittently and where the heater is an air heater and steam is not available to heat the oil.

It is of course common practice to heat the oil even in such apparatus by passing it through a heating chamber equipped with electrical heaters, but between the heater and the nozzle the oil has a chance to cool, even if adequately heated initially, especially Where the burner is operating intermittently. Attempts have heretofore been made to eliminate this difficulty, but these have had various disadvantages. Even if the fuel oil is heated to a point where it can be more efiiectively atomized and burned, this preheating is not sufiicient to raise the temperature to a point where the oil will readily ignite.

It is a primary object of the present invention to provide a simple effective means for heating the oil and keeping it constantly at the desired temperature from the time it leaves the preliminary heater up to and including the atomizing nozzle so that as soon as heat is called for, the oil will be instantly available at the required temperature with no opportunity to cool. A further important object of this invention is to provide for the rapid and intense heating of a small amount of the fuel at the nozzle to a temperature above that customarily secured by the present method of preheating, whereby heavy fuel oil may be readily ignited by an electric spark, eliminating any need for a pilot flame.

A further object of this invention is to provide a fuel oil burner system in which the fuel oil conduit, the air supply pipe, and the atomizing nozzle constitute a resistance heater.

These and other objects and advantages are secured by this invention, as will be more apparent from the following description in which the figure is a schematic diagram of a burner system embodying this invention.

In the diagram, 2 designates a pump which draws oil from a line 3 connected with a source of fuel oil (not shown). The pump has a discharge pipe 4 leading to a preheater 5 where an electric immersion heater or other heating means (not shown) heats the oil to the required temperature. From the preheater 5 the oil enters pipe 6 which has one branch 7 that is connected to the input side of the pump, and which has a pressure relief valve 8 therein. This allows excess fuel oil not required by the burner to circulate through a closed loop in a more or less conventional way.

atent 2,967,923 Patented Jan. 10, 1961 There is a second branch designated 9 leading from pipe 6, to a coupling 10 that has an electrical insulating bushing 11 at the end of pipe 9 and the coupling, this bushing insulating the coupling in from the pipe 9 and the part of the system ahead of the coupling. From the coupling 10 oil flows through pipe 12, solenoid operated on-and-oif valve 13, metering valves 14, and a pipe 15 which preferably includes a coil 16 to give added length, the pipe being wrapped throughout at least most of its length with fiberglass or other heat-resistant insulation, a fragment only of which is shown at 15, both for electrical reasons, and to retain heat. Beyond the coil of pipe 16 the pipe extends to the burner nozzle, the portion of the pipe beyond the coil being designated 17, and the atomizing nozzle being 18. The diagram shows a face plate 20 with a bushing of non-conducting material through which pipe 17 passes, this face plate being at the end of the burner assembly.

The oil is atomized by air under pressure delivered to the nozzle 18, and for this purpose there is a compressor 21 with an outlet pipe 22 that extends through a second insulating bushing in the face plate Zll to the nozzle 18. At 23 there is a bypass loop that includes a pressure relief valve 24. Air from pipe 22 is also carried through a branch pipe 22 to a control valve 25 to actuate an air motor 25 that operates the fuel metering valve 14. In the diagram 1 have shown an insulator 25a in the operating connection between the air motor 25 and the valve 14 to indicate that there is no electrical conducting path from the fuel line to the air line other than the pipes and the other parts forming the duct system to be heated. his is a more or less standard part of the oil burner control, valve 25 being a solenoid operated three-way valve forming part of the burner control system that responds to a thermostat (not shown) and forming no part of the instant invention.

According to this invention a voltage lowering-currentincreasing transformer is provided, this transformer having a primary winding 26, a core 27, and a secondary 23. One terminal of the secondary is grounded on the air pipe 22 at 29, and the other terminal is connected through Wire 30 with the fuel supply pipe 12 adjacent the insulating bushing 11 and at the nozzle side of the coupling 10. By reason of this, the fuel line from coupling it to the nozzle, and the air line from the nozzle to the terminal at 29, all of which is not grounded between the transformer terminals, constitutes a closed electrical circuit for the low voltage heavy current delivered by the transformer. When the transformer is energized, the pipes constituting this circuit, including valves and the nozzle, are heated by their own resistance to the flow of current therethrough. The pipes being of smaller section will be heated more eifectively than the valves, etc., but the heat will be conducted by the pipes and the oil into the larger elements in the circuit, so that from the time the oil passes the coupling it up to and including the nozzle, it will be heated to a desirable temperature for ignition and atomizing. By heating a part of the air pipe, loss of heat from the atomizing nozzle through conduction to the air pipe is eliminated, and in fact the heating of this pipe also helps heat the nozzle. It also provides a convenient return path for the electric current.

The primary of the transformer is connected to the current supply line of the building in which the burner is employed and the supply of current is controlled by a thermostatic switch responsive to the temperature of the oil line. This is shown in the drawing where 31 is one line of the primary current supply and the other line 33 leads through a thermally responsive switch 34 and wire 35 to the other side of the current input. Switch 34 is electrically separate from the ground, as indicated in the diagram by the insulating panel 34 on which the switch is mounted. A thermal element 36 is mounted on the fuel pipe close to the burner, and it is connected through a capillary tube 37 to the switch 34 for actuating the same, the switch and thermally responsive element being well known pieces of equipment. The thermally responsive element is preferably nearer to the burner than to the coupling 10 because this is more remote from the preheater 5 and hence more accurately reflects the temperature of the oil at what would be the coldest point in the system, the nozzle itself perhaps being warmer at times because of its proximity to the combustion chamber.

If the burner is used in space heating apparatus where the demand for heat is intermittent, the fuel in the system beyond the primary heater will be kept at a predetermined temperature but the switch 34 will avoid needles overheating while maintaining the fuel in good condition for ignition and atomizing. As hereinbefore indicated, an important object of the arrangement herein described is to provide in a heated condition a relatively small volume of oil at a temperature where it may be readily ignited by an electric spark. When the burner is operating, oil flows from the preheater 5 quickly enough so that the heating of the pipe and nozzle is relatively less important.

While I have shown and described one embodiment of my invention it will be understood that this is by way of illustration and that the invention is applicable to burners equipped with various types and systems of control.

I claim:

1. A fuel oil burning system comprising a metallic burner spray nozzle, a metal pipe connected to the nozzle through which oil is supplied to the nozzle, a metal air pipe connected to the nozzle and to a source of air under pressure for supplying air to the nozzle for atomizing the oil, means for supplying fuel oil to the first pipe, there being an insulating coupling between said means and the first-named pipe, and a source of low voltage current having one terminal connected to the first-named pipe at a point remote from the nozzle and its other terminal connected to the air pipe, whereby the oil pipe, nozzle and a section of the air pipe form a closed circuit across the terminals of the current source, the said pipes and source of current being so related that the pipes constitute a resistance heater to warm the fluids in the respective pipes and at the nozzle.

2. A liquid fuel burner system comprising a burner nozzle, a pipe for supplying liquid fuel to the nozzle, a source of liquid fuel connected to the pipe, an electric insulation coupling between the pipe and the fuel source, an air supply pipe to the nozzle, and a voltage reducing transformer having one secondary output terminal connected to the first-named pipe and its other secondary output terminal connected with the air pipe, whereby the fuel supply pipe and nozzle constitute a closed circuit across the output terminals of the transformer, the conductivity of the pipes in relation to the low voltage current being such that the pipes constitute resistance heaters for warming the fluids passing therethrough, the reduced voltage reducing shock hazard to one contacting the system.

References Cited in the file of this patent UNITED STATES PATENTS 1,151,586 Herkenrath Aug. 31, 1915 2,224,403 Lines Dec. 10, 1940 2,397,987 Senninger Apr. 9, 1946 2,616,022 Arnaud Oct. 28, 1952 2,802,520 Trabilcy Aug. 13, 1957 

